1 files changed, 72 insertions, 0 deletions
diff --git a/crypto/src/crypto/tls/TlsProtocol.cs b/crypto/src/crypto/tls/TlsProtocol.cs
new file mode 100644
index 000000000..764892d0b
--- /dev/null
+++ b/crypto/src/crypto/tls/TlsProtocol.cs
@@ -0,0 +1,72 @@
+using System;
+using System.Collections;
+using System.IO;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Tls
+{
+    public abstract class TlsProtocol
+    {
+        /**
+        * Make sure the Stream is now empty. Fail otherwise.
+        *
+        * @param is The Stream to check.
+        * @throws IOException If is is not empty.
+        */
+        protected internal static void AssertEmpty(MemoryStream buf)
+        {
+            if (buf.Position < buf.Length)
+                throw new TlsFatalAlert(AlertDescription.decode_error);
+        }
+
+        protected internal static IDictionary ReadExtensions(MemoryStream input)
+        {
+            if (input.Position >= input.Length)
+                return null;
+
+            byte[] extBytes = TlsUtilities.ReadOpaque16(input);
+
+            AssertEmpty(input);
+
+            MemoryStream buf = new MemoryStream(extBytes, false);
+
+            // Integer -> byte[]
+            IDictionary extensions = Platform.CreateHashtable();
+
+            while (buf.Position < buf.Length)
+            {
+                int extension_type = TlsUtilities.ReadUint16(buf);
+                byte[] extension_data = TlsUtilities.ReadOpaque16(buf);
+
+                /*
+                 * RFC 3546 2.3 There MUST NOT be more than one extension of the same type.
+                 */
+                if (extensions.Contains(extension_type))
+                    throw new TlsFatalAlert(AlertDescription.illegal_parameter);
+
+                extensions.Add(extension_type, extension_data);
+            }
+
+            return extensions;
+        }
+
+        protected internal static void WriteExtensions(Stream output, IDictionary extensions)
+        {
+            MemoryStream buf = new MemoryStream();
+
+            foreach (int extension_type in extensions.Keys)
+            {
+                byte[] extension_data = (byte[])extensions[extension_type];
+
+                TlsUtilities.CheckUint16(extension_type);
+                TlsUtilities.WriteUint16(extension_type, buf);
+                TlsUtilities.WriteOpaque16(extension_data, buf);
+            }
+
+            byte[] extBytes = buf.ToArray();
+
+            TlsUtilities.WriteOpaque16(extBytes, output);
+        }
+    }
+}